In recent times, national attention has been focused upon methods to conserve energy resources, particularly fossil fuels which comprise a non-renewable source of energy. One of the principal possible sources of additional energy is energy received from the sun, commonly referred to as "solar energy."Recent attention has been directed to phase change materials, such as an aqueous mixture of glauber salts, as a material useful in collecting solar energy during sunlight hours and emitting such energy during the nighttime. Additionally, such phase change materials are capable of collecting excess heat energy which may occur in a building structure. Such phase change materials have the capability of being solid at normal room temperatures but melting at such normal room temperatures when subjected to the sun's rays to thereby absorb heat energy. Thus, during the daytime, the phase change material will absorb sun energy and other excess heat energy. During the nighttime, when there is no sun energy and the normal room temperature begins to decrease, the phase change material will revert from liquid back to solid and in the process emit the heat which was previously stored. Thus, the stored energy is given off during the nighttime when it is needed.
One problem with such phase change material has been that, being incongruent aqueous mixtures, there is a tendency for the constituents of the mixture to separate under the force of gravity after undergoing a few hundred freeze-thaw cycles. It has been learned, however, that if the mixture is contained in layers of about one-quarter inch or less, the number of freeze-thaw cycles which the material may undergo is greatly increased. Thus, it becomes practical to make the container for the phase change material in the form of a building element, such as a floor or ceiling tile in a house. When used as a floor tile, such a building element may absorb sun rays directly through windows and glass doors of a house during the day. Sunlight may be reflected to the ceiling tiles by means of a reflective louver device similar to an upside down venetian blind placed exteriorly of the house.
In accordance with the present invention, we have provided structures for incorporating such phase change materials into tiles, for use either as ceiling or floor tiles. This results in use of the tiles as building materials as well as for heat absorbing. Thus, the cost of the panels is prorated between two functions resulting in making them economically attractive.